The present invention refers to devices for filtering of the air used in the air-fuel mixture supplied to the internal combustion engine.
Particularly the invention refers to a device for filtering the intake air of supercharged and aspirated internal combustion engines.
As known in the automotive field the air filtering has particular importance since causes the gasoline and air mixing and therefore the so obtained fuel mixture used in the combustion.
The intake air therefore must be filtered for removing any impurities that may clog or wear and damage the inner members of the motor.
The air filters are normally flattened, cylindrical or conical shaped and are contained in a related housing which is in flow communication with the air intakes through an aperture and allows the filtered air outflow through a further opening.
Document GB 467,194 discloses a filtering device including a tubular housing for a filter fixed to a support mean provided with an inlet opening and supporting the tubular housing. In said device the air flow pass through the filter in a non homogeneous manner. Document U.S. Pat. No. 5,888,260 discloses a filtering device provided with a conical filter having an inner air deflector spherically shaped and providing a low efficiency flow deflection. The conical filter is housed in a single body tubular housing without allowing the disassembly of the filter from the outlet.
The known filters for the use in sporting engines, the so-called xe2x80x9csprint filterxe2x80x9d, have polyester filtering cartridges, whose ends have heavy polyurethan flanges and/or caps that are extremely expensive and further cannot withstand temperatures greater than 90xc2x0 C., because of the used material. These filters have generally truncated cone shaped and they are contained in metallic containers shaped as almost conic or truncated-conic segments: the drawback of such containers consist in lacking of the air thermally insulation since such containers transmit an excessive heat to the air.
The known filters with the paper filtering cartridges ensure a good filtration, because they hold particles greater than 10 microns, but they have the drawback of an excessive flow resistance for the air flow.
The filters with polyurethan filtering cartridges have a low filtering with a consequent acceptable flow resistance, but they have the drawback connected with the so-called xe2x80x9csponge effectxe2x80x9d in presence of high humidity, conditions happening in the areas with continental climate, creating consequently technical problems for the sporting engines, using these kind of filters.
Another drawback of the known sprint filters consists both in the reduced inner volume of the external filter housing, mostly due to the conic shape of this latter, and in the insufficient filtering surface, due to the conic shape of the filter with wide inclination angles.
Another drawback of the known filters consists in the speed increase of the air passing through the conic container with variable geometry and therefore in a reduction of the filtering capacity.
The main object of the present invention is to propose a filtering device for the intake air of internal combustion engines fit to operate at temperatures up to about 250xc2x0 C. and at the same time to thermally isolate the air flow passing through it and filtered.
Further object is to propose a device without xe2x80x9csponge effectxe2x80x9d in high environmental humidity conditions and however characterized by low flow resistances, by an high air filtering value and by a low production cost.
Further object consists in providing a device reliable having a life greater than a distance of about 300,000 km, however usable with a very low maintenance and easy to dispose because primarily made of a natural material.
Another object is also to propose a device having small external dimensions still preserving the most wide internal volume.